Rickey Henderson was recently offered $1 million by the Golden Baseball League, to enter the Hall of Fame wearing a San Diego Surf Dawgs hat. You can read the entire press release here.
Rickey played one year for the Surf Dawgs in 2005, the inaugural year for the GBL, and actually won the GBL championship. That championship game was Rickey's last in "professional" baseball, before he finally decided to hang up the cleats.
Unfortunately for the GBL, and fortunately for me, the Hall of Fame now has the final say as to what cap the players will wear in their HOF plaque. The player is asked for their preferred choice, but they do not have the final decision.
The A's already lost Reggie Jackson to the Yankees (when he decided against wearing an A's hat), and there's no way that something like that should happen again. When you think of Rickey, you think of the A's (at least, I do), and that's the way it should continue to be.